The Jehovah's Witnesses are selling three Brooklyn properties, including one building with its iconic Watchtower sign and clock, that could be worth almost $1 billion, according to an estimate.

The religion's global headquarters are in Brooklyn Heights, but the Witnesses are moving upstate to Warwick in Orange County. Almost 4,000 volunteers are constructing their new upstate home, expected to open in the fall of 2016, according to a release.

One of the properties the Witnesses are selling is 85 Jay St., which is a 135,000-square-foot parking lot near the Manhattan Bridge.

"The site spans an entire city block in the dynamic Dumbo neighborhood, and has nearly 1 million square feet of development rights," said spokesman Richard Devine in a statement.

The Witnesses' headquarters is at 25-30 Columbia Heights, and they also are looking for a buyer for 124 Columbia Heights, a 10-floor residential building near the promenade.

The Downtown Brooklyn Partnership said the sale of the three properties could be close to $1 billion in total, and more when other recent sales are included. The Witnesses have not yet set a price.

"The 85 Jay St. [property] is incredibly valuable," said Tucker Reed, president of the partnership. "Ground-up development opportunities in Dumbo are pretty much gone today. Pricing will make it difficult for many, but I would expect big numbers. They aren't making any new land in Dumbo, one of [the] city's most desirable neighborhoods."

The partnership hopes the Witnesses will give back some of the money they make in the sale to the borough, such as a gift for parks or schools in Brooklyn. The sale could bring in a lot of new residents and companies to the area.